1. Field of the Invention
The present invention relates to a scheduling apparatus dynamically performing job scheduling in a parallel computer system.
2. Description of the Related Art
In a conventional parallel computer system, job scheduling is performed to efficiently use computer resources such as a CPU (Central Processing Unit), memory, etc. Here, the minimum unit of a program executed in a computer system is defined to be a process, and a unit executed in parallel as a process complex is defined to be a job.
As a scheduling method such as management of a job queue waiting to be processed, the following methods are mainly used.
(1) Successive insertion/execution operations of jobs according to FIFO (First In First Out)
(2) Sorting (scheduling) operation of jobs within a queue according to priorities
With the method (2), a priority flag, etc. is attached to each job. Even if a job is inserted in a queue later, control such that the job is inserted in the beginning of the queue is performed if its priority is high. In addition to these methods, various scheduling methods were proposed to insert a job.
However, the above described conventional scheduling methods have a problem of being unable to cope with associated uncertainties after job insertion.
When a job is to be executed, it is difficult to accurately grasp an actual execution time prior to execution. This is because job execution includes uncertainties such as a conflict of resources between one process and a different PE, an external input/output, etc., if control by an OS (Operating System) is assumed.
In this case, if scheduling is performed with a scheduling method which does not accurately manage an execution time, a scheduling error becomes larger as job execution proceeds. As a result, a situation where a load imbalance occurs in a particular PE (Processor Element) occurs, leading to an inefficient use of the parallel computer system. Furthermore, as long as an OS manages a plurality of processes, an occurrence of a scheduling error caused by such uncertainties is inevitable.